Field of the Invention
This disclosure relates to a vibration type actuator configured to bring a moving body into press contact with a vibrator for frictional drive.
Description of the Related Art
In general, a vibrational wave motor as a type of a vibration type actuator includes a vibrator configured to form a progressive vibrational wave and a moving body configured to come into press contact with the vibrator, and is configured to get a drive force by frictionally driving the vibrator and the moving body with the progressive vibrational wave. Therefore, a contact portion arranged between the vibrator an the moving body comes into and out of contact with the vibrator repeatedly while being deformed in accordance with the vibrations of the vibrator to extract the drive force.
However, when the moving body and the vibrator are directly influenced by an external force from a driven member of the vibration type actuator, contact between the vibrator and the moving body becomes unstable. Consequently, uneven speed and generated force, local abrasion, and a noise, which is referred to as so-called squealing sound, may result.
Therefore, a vibrational wave motor in which an output shaft is fixed by a bearing to resist an influence from an external force is proposed (for example, see Japanese Patent Laid-Open No. 2012-125070, (corresponding U.S. Patent No. 2012/146460)). The vibrational wave motor of this type is illustrated in FIG. 5.
In FIG. 5, a vibrator 102 fixed to a base 101 has a ring shape, and an upper portion of an elastic member 102b is provided with a plurality of projections 102d over an entire circumference thereof.
A piezoelectric ceramics 102a is adhered to a bottom surface of the elastic member 102b with an adhesive agent, and generates a progressive vibrational wave by being applied with two AC voltages having a phase difference by a drive circuit, which is not illustrated, when the motor is driven.
A moving body 103 includes a contact portion 103c having a frictional surface that comes into frictional contact with the projections 102d of the vibrator 102, and is allowed to contact stably with the vibrator 102.
A pressure receiving member 104 and a press member 105 are mounted on an upper surface of the moving body 103. An inner peripheral portion of a press spring 105b of the press member 105 is mounted on a disk 105a thermally inserted onto an output shaft 108 to transmit a drive force of the moving body 103 to the output shaft 108.
The output shaft 108 is rotatably supported by a pair of ball bearings 109a and 109b, and an inner ring of the ball bearing 109a is applied with a pressure by an extent corresponding to a displacement amount of the press spring 105b for bringing the moving body 103 into press contact with the vibrator 102 at an adequate force in advance. Accordingly, rattling of the ball bearing 109a in a radial direction is restrained, and hence swinging of the output shaft 108 in the radial direction may be restrained. The position of a direction of rotation axis of the output shaft 108 is fixed to the pair of ball bearings 109a and 109b. Accordingly, even though the output shaft 108 is subjected to an external force from the driven member in the direction of rotation axis of the vibration type actuator, which is no illustrated, the external force is absorbed by the ball bearings 109a and 109b, and little external force is applied to the vibrator 102 and the moving body 103, whereby stable drive of the vibration type actuator is achieved.
An aspect of this disclosure relates to a vibration type actuator configured to restrain an influence from an external force from a driven member of the vibration type actuator and to allow a reduction in thickness.